title: Method for the in situ calibration of a passive phosphate sampler in estuarine and marine waters.
abstract: Passive samplers for phosphate were calibrated in the laboratory over a range of flow velocities (0-27 cm s(-1)) and ionic strengths (0-0.62 mol kg(-1)). The observed sampling rates were between 0.006 and 0.20 L d(-1). An empirical model allowed the estimation of these sampling rates with a precision of 8.5%. Passive flow monitors (PFMs), based on gypsum dissolution rates, were calibrated for the same range of flow velocities and ionic strength. Mass loss rates of the PFMs increased with increasing ionic strength. We demonstrate that this increase is quantitatively accounted for by the increased gypsum solubility at higher ionic strengths. We provide a calculation scheme for these solubilities for an environmentally relevant range of temperatures and salinities. The results imply that co-deployed PFMs can be used for estimating the flow effect on the in situ sampling rates of the phosphate samplers, and we expect that the same may hold for other passive samplers.
authors.affiliation: The University of Queensland, National Research Centre for Environmental Toxicology (Entox), 39 Kessels Road, Coopers Plains, Queensland 4108, Australia. d.obrien2@uq.edu.au
authors.forename: Dominique S
authors.initials: DS
authors.lastname: O'Brien
authors.forename: Kees
authors.initials: K
authors.lastname: Booij
authors.forename: Darryl W
authors.initials: DW
authors.lastname: Hawker
authors.forename: Jochen F
authors.initials: JF
authors.lastname: Mueller
mesh_terms: D002133:Calcium Sulfate / Q000032:analysis / Q000737:chemistry; D002138:Calibration; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D005618:Fresh Water / Q000737:chemistry*; D009994:Osmolar Concentration; D010710:Phosphates / Q000032:analysis* / Q000592:standards; D012623:Seawater / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000592:standards
chemical_list: D010710:Phosphates; D014874:Water Pollutants, Chemical; D002133:Calcium Sulfate